A brush-type sweeper uses a cylindrical brush rotating about a horizontal axis to sweep debris from a surface and throw it into a debris hopper on the machine. The efficiency of this throwing action is never quite 100 percent, though, and a small percentage of the swept debris follows a path around the circumference of the brush, up and over it and into the space behind it. The exact causes of this circumferential travel are not well understood, but the fact that it happens is well known.
Early brush-type sweepers left this overthrown debris behind them in an unsightly fashion on the swept surface. Then it was found that if the rear wall of the brush housing was extended down nearly to the floor and sloped forward under the lower part of the cylindrical brush and as close as possible to it, most of the overthrown debris could be deflected into the brush, whch would recirculate it and throw most of it into the debris hopper. Thus the recirculation flap, as this sloping rear wall was called, substantially improved the sweeping efficiency of the machine. Consequently recirculation flaps have been in common use for many years.
One problem in using sweeping machines is that there are often high areas on floors, such as lifted concrete slabs, speed bumps, ramp crests etc., which project up and can damage machine parts close to the floor. This problem has been especially troublesome with recirculation flaps, because they are not only close to the floor, but they point forward and they extend across nearly the full width of the machine, so they tend to catch on any floor projection anywhere in the path of the machine. They generally consist of a strip of stiff rubber sheet stock extending forward and down from the rear wall of the brush housing, with the rear edge of the flap being bolted to a flange at the lower edge of the housing. This steel flange must be fairly close to the floor to support the flap in a position where it will be effective. When a low floor projection is encountered, the rubber flap may catch on it and bend back without damage, then flip forward into position again after the projection is past. A higher projection, however, will often catch the steel housing flange, with the usual result that the rear brush housing wall is bent out of shape, the recirculation flap is distorted or torn off, and an expensive repair job is needed to restore the machine to good working condition.
From all of this it will be evident that there is a long standing and unsolved need for a recirculation flap and mounting means for it that can withstand floor projections as high as a speed bump without being damaged and remain functional after encountering such projections. The present invention is directed toward that end.